With conventional band links, a user adjusts the length of the band using the band link. However, conventional band links as described above include several disadvantages in that the band is not well secured and may slip from the band link if some shock or force is exerted on the band link after using. Thus, the user is required to inspect the band and the band links. In addition, the thickness of the folded band portion is thicker than that of the controlling piece of the band link or buckle. As a result, the band portion will protrudes above the surface of the band links. An example of a conventional band link partially ameliorating such defects is disclosed in Korean Utility Model Patent Application No. 92-1278 entitled "Band link With A Safety Device." The band link disclosed there includes some of the same inherent defects as other conventional devices in that if the band is inserted in the band link and then locked by a locking piece it may not loosen, but its thickness increases with use of a band-inserting bar in the locking piece. Further, because the locking piece is separately assembled with the band link, the separate pieces may be lost or damaged by mistake in use.